Then his popularity started a long, steady decline. The Iraq war divided the country, particularly after claims about weapons of mass destruction proved false. Bush's support for a path to citizenship for illegal immigrants alienated Southern conservatives. The religious right, a voting bloc that twice helped elect him to office, fractured amid a growing sense that Bush had failed to deliver on a range of cultural issues.

Meanwhile, fiscal hawks watched with dismay as government grew and deficits soared. Finally, say political analysts, the administration's response to hurricane Katrina exposed an ill-prepared bureaucracy staffed by political appointees, like Michael Brown, director of the Federal Emergency Management Agency, with few qualifications for the job.

"When did Bush lose his mojo? I think Katrina was the turning point," says Princeton historian Sean Wilentz, author of "The Age of Reagan." "Even after the Iraq war, he had just enough credibility left, because Democrats were seen as so weak on defense and national security. "But 2005 [the year Katrina hit] was a disaster for Bush. He seemed to be ineffective, and his subordinates seemed to be manifestly incompetent. You had an X-ray into how the administration was working – and not working."